pErk and DNA-PKc form a complex that requires the presence IEX-1. (A) NHEJ activity in WT and Iex-1^−/− LSK cells cultured in complete medium in the presence or absence of U0126 (10 μM). The experimental procedure (left) and means + SEM percent of GFP⁺ cells in LSK DsRed⁺ cells (right) are shown. Each dot represents an individual mouse. (B,D) PLA between pErk and DNA-PKc in WT and Iex-1^−/− LSK cells. Cells were cultured in complete medium for 30 minutes and analyzed 30 minutes after IR (2 Gy) or not. Representative pictures (×100) and means + SEM of PLA dot numbers per cell (left) and percent of cells with the indicated amounts of dots (right) are shown. (C) UT7-Mpl cells were treated with TPO and then irradiated (2 Gy). Thirty minutes after IR, nuclear extracts were immunoprecipitated with anti-DNA-PKc or control (c) mouse immunoglobulin G. NIR, no IR.